These 15 frugal billionaires have answered that question for real, and their response is "not much."

Instead of dropping dough on jets, yachts, and mansions, they have saved up, lived modestly, and given away huge amounts of money to charity.

1/

Warren Buffett, chairman and CEO of Berkshire Hathaway

Net worth: $46 billion

Buffett still lives in the Omaha, Nebraska, home he bought for $31,500 more than 50 years ago.

He doesn't own a yacht because, as he puts it, "Most toys are just a pain in the neck." When he married his second wife, rather than a lavish affair, it was a brief afternoon wedding at his daughter's house in Omaha.

Cheriton called himself "spoiled" for taking a windsurfing vacation in Hawaii, and in a recent Forbes profile said that his biggest recent splurge was his 2012 Honda Odyssey.

6/

Karl Albrecht, co-founder of Aldi

Net worth: $25.4 billion

Aldi is to Europe what Walmart is to the US. Albrecht founded the company with his late brother Theo, and together the two made billions building the notoriously no-frills chain.

Raised by a shopkeeper mom and a miner father, they remained true to the vision of frugality that drove both their stores and their lives. When Theo was kidnapped for 17 days in 1971, his brother negotiated a bargain ransom of $4 million — which he then wrote off as a business expense.

7/

Christy Walton, heir to Walmart fortune

Net worth: $27.9 billion

Walton is the widow of John T. Walton, one of the sons of Walmart founder Sam Walton.

Despite their wealth, Walton wanted a normal upbringing for her son, so she raised him in an 1896 Victorian home in National City, Calif., outside of San Diego.

After her husband died in a plane crash, Walton donated the home to the International Community Foundation - Center for Cross-Border Philanthropy.

8/

Ingvar Kamprad, founder of IKEA

Net worth: $3 billion

The founder of IKEA said he drove 15-year-old Volvo and always flew economy class, according to a 2006 Reuters article.

His frugal ways extend to his home in Switzerland, which is reportedly decorated mostly with inexpensive IKEA furniture, as well as a few family heirlooms.

According to The Daily Mail, Kamprad and his wife are often seen eating in cheap restaurants and haggling over prices at the market.

And by all accounts his lifestyle hasn't changed since his early days in business.

"Money is just a way for Tony to get to his endgame," said Erik Moore, an early Zappos investor. "Money just doesn't matter to him. If he only had a million dollars left, he'd spend $999,999 to make Vegas work. He would be just as happy with a dollar in the bank and being around people he cares about and care about him."

10/

Alexander Lebedev, Russian businessman

Indeed, the most striking difference between him and other oligarchs is his social activism. Lebedev has used his large fortune to improve the lot of ordinary Russians. He talks enthusiastically about such unfashionable themes as flat-pack housing and potatoes.

Jim C. Walton, Walmart heir and chair of Arvest Bank

Walton may belong to one of the wealthiest families in the world, but he has followed in the frugal footsteps of his father, Walmart founder Sam Walton.

The youngest and most private of the Walton siblings, Jim still resides in Bentonville, Ark., where he runs the family's personal wealth management company from the upstairs office of " a plain old brick building" in downtown Bentonville.

David Green, founder and CEO of Hobby Lobby

While he could easily afford a Gulfstream of his own, Green, founder of arts and crafts retail chain Hobby Lobby, prefers to fly coach.

Instead of spending his billions on himself and his family, Green has famously become the largest individual donor to evangelical causes in America. He's given upwards of $500 million in charitable contributions over his lifetime, according to Forbes.